The needs of today's electronic industry require higher speed electronic equipment such as computers and the like. Since many of the electrical interconnections within this type of equipment use circuit boards, it is desirable to provide high-speed card edge connectors having a controlled impedance that will essentially match the impedance of the circuit boards. A high-speed connector is one that can pass fast rise time signals without distorting or degrading that rise time. It is desirable, therefore, to control the impedance of the connector to reduce signal reflection caused by changes in impedance in the pathways conducting the digital pulse. Impedance control includes controlled spacing of ground and signal traces and interconnections. With the closer spacing of the conductors, it is also necessary to prevent cross talk between adjacent conductors.
U.S. patent application Ser. No. 07/458,071 discloses a card edge connector for use with a circuit card of the type having ground contact means disposed along a leading edge of the card and signal traces having contact means located rearwardly from the ground contact means. The connector includes a housing member having a plurality of contact receiving passageways including contact locations spaced laterally along a card receiving cavity. Each passageway has a pair of opposed signal contact members and a discrete ground contact member disposed therein, the ground contact member being positioned between the pair of signal contact members. Owing to the position of the ground and signal contact means on the circuit card and the corresponding contact sections of the signal and ground contact surfaces, the contact surfaces of the signal contact members temporarily engage the ground contact means of the card during insertion of the circuit card into the connector. Thus it is important that an electrical system not be energized during the insertion or withdrawal of the daughter card from the connector. It is desirable, therefore, to have a connector having the same desired electrical characteristics that permits insertion and/or withdrawal of daughter cards while the electronic system remains energized.
U.S. Pat. No. 4,659,155 discloses a two-piece daughter board-backplane connector having an internal connector for use with a circuit board having an internal ground plane layer. The daughter board element is connected to a multilayer impedance controlled daughter board having internal ground layers and signal conductors on opposed surfaces. The signal contacts on the board are electrically engaged with rows of signal contacts disposed on opposite sides of the daughter board. The ground contacts are mounted between dielectric portion of the connector element and overlap a plurality of signal contacts on a backplane connector element. The ground contacts overlap a plurality of adjacent signal contacts. The daughter board connector includes a plurality of receptacles for receiving pin members on the backplane element. One disadvantage of the above connector is that it is a two-piece assembly that requires a considerable amount of space to accommodate all of the components of the assembly. Furthermore the connector has a number of different parts, which require a number of manufacturing steps to produce the assembly, thereby increasing the cost of the finished product. It is desirable, therefore, to provide a means for assuring a ground contact closely associated with signal connections in a compact and cost effective one-piece connector.
U.S. Pat. No. 3,399,372 discloses a high density connector package having a plurality of signal and ground contacts arranged in an alternating array such that each signal contact is associated with a ground contact. In the disclosed embodiment, the signal contacts are small wire members and the ground contacts are metal sheet members thereby providing for close stacking of the signal and ground pairs. The disadvantage of the alternating contact type of system is that for signal contacts to be maintained at a given center line spacing, the dimensions of the various internal members of the assembly must be "scaled down" to provide for "double density", that is that two adjacent contacts must be accommodated in the space previously occupied by a single contact member.